Author Topic: Easy OTC benzaldehyde? (Read 804 times)

Assyl Fartrate · « **on:** March 07, 2012, 04:10:23 PM »

Never heard of it being tried... criticism welcome. Maybe this could be made to work.

Load up a large 2 neck RB with toluene, and an addition funnel with KMnO4 solution... throw in a stir bar and get it whipping it up. Set up for reflux, stuff some glass wool near the bottom of the column, and fill it with sodium bisulfite crystals. Get a heavy reflux going... at first the bisulfite will be getting washed with toluene, then as the addition of KMnO4 begins, benzyl alcohol and benzaldehyde. Benzaldehyde forms a solid adduct with bisulfite... it'll be retained in the column and not get oxidized to benzoic acid. Then just dump out the adduct into aqueous NaOH and decant the benzaldehyde...

Everything is cheap, OTC, and available by the kilo...

Edit by Vesp: Next time provide references (such as how the KMnO4 goes about oxidizing the Toluene into benzaldehyde), how the bisulfite would form the adduct, and also try to be a bit more explicit on how you forsee the reaction going, the equipment used, and so on. The more detailed and more researched the original post is - the easier it will be for others to spot the issues, understand the reaction, and point one another in the correct direction.

lugh · « **Reply #1 on:** March 07, 2012, 04:44:03 PM »

The chemical industry would be doing it that way if it were that easy, the primary result will be benzoic acid

The attached article J. Chem. Soc 555-560 (1955) goes into more detail as to why this happens

Assyl Fartrate · « **Reply #2 on:** March 07, 2012, 05:18:20 PM »

It wouldn't be cost effective for them to do something like that... it would only be worth it with the high profit margins of clandestine chemistry.

You can make acetaldehyde by oxidation of EtOH with KMnO4, simply by distilling off the acetaldehyde as it's formed.

Acetaldehyde's bp is 20C, EtOH's is 78C. Good separation there. Not so good here though... benzaldehyde's bp is 178C, benzyl alcohol's is 205C.

That's not the big issue though... the thing is, with EtOH oxidation you're starting with something with a higher BP than the product, so you can just distill off the top and be done with it. Here, you're started with toluene, which has a much lower BP than benzaldehyde. If you started with benzyl alcohol you may be able to copy the EtOH procedure, but toluene is far more available. If you distill off the top here you'd just remove the toluene and put a quick end to the fun. The idea of the bisulfite is the same as distilling off the top - remove a product from the system so that it doesn't decompose. The real question is whether the vapor pressure of the benzaldehyde is going to be high enough at the BP of toluene to get it up into the column.

lugh · « **Reply #3 on:** March 07, 2012, 05:30:47 PM »

Chemical industry found the best solution to all of these issues many decades in the past by means of the Loomis and Benedetti patents

That reaction sequence involves OTC materials

Vesp · « **Reply #4 on:** March 07, 2012, 11:20:29 PM »

I like this idea - I wonder if it would work? Any reason to think it wouldn't work at all?

It might be low yielding, but it still might produce a decent amount of benzaldehyde.

You can also form hydrobenzamide with benzaldehyde + ammonia and it is supposed to be reversible. Perhaps that is worth keeping in mind.

lugh · « **Reply #5 on:** March 08, 2012, 02:36:46 AM »

Chemical industry has known that the redox reaction would be a serious complication for a century

Perhaps the attached article, J. Org. Chem., 35 pp 982–985 (1970) will clarify matters

Assyl Fartrate · « **Reply #6 on:** March 08, 2012, 09:16:29 PM »

KMnO4 oxidizes EtOH to AcOH as well. But you have to remember it is a stepwise process. It doesn't go directly EtOH -> AcOH, nor does it go directly PhCH3 -> PhCOOH. The aldehyde is the intermediate in each case, and if it can be removed from the reaction mixture (the oxidant) as it's formed, you can get good yields. NaHSO3 is only oxidized to NaHSO4 when it's exposed to an oxidant. KMnO4 is a solid in the RB, NaHSO3 is a solid in the column. They would never come into contact. Again the big question is whether the vapor pressure of benzaldehyde will allow it to be carried into the column when the toluene is refluxing.

lugh · « **Reply #7 on:** March 08, 2012, 10:36:34 PM »

Some other references relevant to this discussion are:

US613460

and

J. Chem. Soc. pp 1379-1381 (1951)

Sedit · « **Reply #8 on:** March 10, 2012, 07:44:26 AM »

This is the type of reaction that instead of starting a thread saying, "Hey, this would be cool if it worked...."

It would be much better if it was performed and the results reported. There is to much speculation and not enough experimentation anymore.

Don't you people really like playing with chemicals or do you all just like talking about them? I for one think an explosion is much more exciting to watch then it is to describe it to someone else.

Please, can we see some mother fucking work done around here for a change?

Edit by Vesp: This is a really great point. But also it is good to get an understanding of the process before you do it, as was the case here.

Assyl Fartrate · « **Reply #9 on:** March 10, 2012, 08:20:35 AM »

No lab equipment, no chemicals, and everything needed prescribed. Just trying to give some things to try for those who are equipped.

lugh · « **Reply #10 on:** March 10, 2012, 01:06:05 PM »

Quote

Don't you people really like playing with chemicals or do you all just like talking about them? I for one think an explosion is much more exciting to watch then it is to describe it to someone else.

Please, can we see some mother fucking work done around here for a change?

Pressure will rupture a column

These people need to study basic physics and chemistry until they understand it before they even try doing any real lab work

Quote

No lab equipment, no chemicals, and everything needed prescribed. Just trying to give some things to try for those who are equipped.

You left out your number one deficiency, knowledge and understanding of basic physics and chemistry

Your proposed synthesis is ass backwards, as manganese dioxide is formed when potassium permanganate and sodium bisulfite interact as is mentioned in the articles already uploaded in this thread and in articles already present on this web site

You will probably need to study physics and chemistry for a very long time before you're going to be able to come up with a novel synthesis of something simple like benzaldehyde which has numerous commercial uses and is thus quite valuable compared to toluene

Instead of wasting members' time and resources and endangering them you could have read the attached review article which has been available online since the days of the Hive

This thread is being locked since it's futile and dangerous

You also should have read the wikipedia articles:

The other main use of sodium bisulfite is as a mild reducing agent in organic synthesis in particular in purification procedures. It can efficiently remove traces or excess amounts of chlorine, bromine, iodine, hypochlorite salts, osmate esters, chromium trioxide and potassium permanganate.

h**p://en.wikipedia.org/wiki/Sodium_bisulfite

h**p://en.wikipedia.org/wiki/Bisulfite

which would have given you a clue as the redox reaction

The end results from the effort applied

Vesp · « **Reply #11 on:** March 10, 2012, 08:33:12 PM »

Unlocked because I think this is a decent topic. Locking something because a dangerous idea is discussed is rather stupid. Everything is dangerous. Talk about how to make it safer then just shutting the door on the idea. Also all ideas are dangerous - it would be better to discuss the issues involved that make it dangerous, and give a nice walk through to those who do not understand or see the same issues as other members...

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The sodium bisulfite is not ever in contact with the permanganate, as clearly stated several times...

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Quote

Your proposed synthesis is ass backwards, as manganese dioxide is formed when potassium permanganate and sodium bisulfite interact

Lugh, How do you propose the KMnO4 will interact with the bisulfite when they are separated?

Maybe the KMnO4 isn't the best oxidant, maybe something like a hypochlorite would be better -- I don't know, but I think this topic is worth discussing. If pressure build up is an issue, consider a method to prevent any danger involved with pressure build up - assuming the forming adduct of benzaldehyde and toluene is even an issue.

Also - who cares about "the chemical industry" this might work well for someone who.. doesn't have access to a chemical industry - The nitroethane thread certainly isn't talking about the most economical, chemical industry approved method, and it even discusses some dangerous ideas.

Also lugh, stop making little jabs at members. I have yet to assign that task to any members and I do believe there is a rule that states... "Keep all discussions professional. Do not personally insult other members. Regardless if the person is a lacking in chemical and physical understanding it doesn't matter as long as they are decent about it, and have done their research. Comments such as "You left out your number one deficiency, knowledge and understanding of basic physics and chemistry " are not conducive to creative discussion and helping the community think laterally to come up with new and innovative ways to obtain and produce precursor chemicals.

If a comment has to be made, it is better to walk them through their entire process and explain how it will not work, or possible issues it might run into, instead of just simply say they do not know enough. When someone is posting an idea as a possible, or potentially viable route to something, and asking for criticisms... of course they do not know.

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I think very few people are understanding that the sodium bisulfite and the KMnO4 are never in contact with one another, or that another oxidizer could be used instead.

Personally, I do not think this reaction will work well enough to use it as a means to getting benzaldehyde. I suspect the water that would be added to the heated toluene to give a KMnO4 solution will lead to some issues as the water will evaporate and dissolve/absorb into the sodium bisulfite crystals in the column. This will either cause the bisulfite to drip back in, or clog - but perhaps a column isn't the answer and this issue could be remedied. I bet it is complex though. Perhaps having a solution of the bisulfite directly contact the toluene, but not the KMnO4 solution would work - but that complicates the hell of out things.

Instead of this being a synthesis for benzaldehyde, it might be more effective as a means to producing and collecting Acetaldehyde, Formaldehyde, and other such compounds. Though, the solubility of sodium bisulfite in alcohol will likely be an issue, if it is soluble in alcohol - as it would drip back in..

Assyl Fartrate · « **Reply #12 on:** March 10, 2012, 10:54:54 PM »

Quote

I suspect the water that would be added to the heated toluene to give a KMnO4 solution will lead to some issues as the water will evaporate and dissolve/absorb into the sodium bisulfite crystals in the column. This will either cause the bisulfite to drip back in, or clog - but perhaps a column isn't the answer and this issue could be remedied.

This is a good point - useful critique, thanks.

atara · « **Reply #13 on:** March 11, 2012, 12:37:42 AM »

Isn't benzaldehyde naturally present in almond extract? Wouldn't that be easier?

http://www.freepatentsonline.com/1416128.pdf

I imagine anyone looking for a bulk synthesis is not going to be making their own benzaldehyde anyway. Small-scale, hydrolyzing amygdalin seems like the easiest option.

Assyl Fartrate · « **Reply #14 on:** March 11, 2012, 12:51:07 AM »

You are correct... except it's fake stuff, not real extract... but yeah, it's in every supermarket in the states.

lugh · « **Reply #15 on:** March 11, 2012, 01:06:58 AM »

The proposed apparatus involves heating toluene and potassium permanganate in a closed container, presumably a round bottom borosilicate glass flask

A column with a plug of glass wool and a rag impregnated with sodium bisulfite is attached to the neck, and supposedly benzaldehyde is going to react to form an adduct

As noted, objections to this are:

1) Potassium permanganate doesn't oxidize aromatic side chains to aldehydes, the product in this case would most likely be benzoic acid not benzaldehyde

2) The sodium bisulfite has to be dissolved in water to form the adduct

3) If the glass wool plug and rag allow the toluene to go through, the sodium bisulfite will be washed down into the flask by percolation, at least here on Earth where there's this physical phenomenon called gravity

4) The most likely result of this madness is that the glass wool and rag will plug the column, and hot toluene will be ejected as the column takes off like a rocket

as far as oxidations:

A complete source of information on oxidations of organic compounds, with emphasis on preparative aspects and results. Important features include: discussions on oxidizing agents and on oxidation reactions using them; correlation tables showing what oxidizing agents are suitable for conversions of particular compounds to their oxidation products; and a collection of typical laboratory procedures for the main types of oxidations. All information is supported by examples, thorough referencing, and indexing.

Oxidations in Organic Chemistry by Milos Hudlicky:

http://bookfi.org/dl/541498/ea51fd

which was scanned long ago by yours truly for the purpose of educating the swarm

Unfortunately the new generation can't apparently be bothered with reading what took so much time, effort and treasure to make available

Assyl Fartrate · « **Reply #16 on:** March 11, 2012, 02:21:04 AM »

The column plugging is a legitimate concern - good point. Thank you for bringing this up. Perhaps it would be possible to design an apparatus that involves an open column, and a condenser dripping into a column packed with NaHSO3, to avoid a risk of Mount Vesuvius visiting the kitchen. But toluene being oxidized directly to benzoic acid is doubtful. Again, oxidation is generally a stepwise reaction. Alkane->alcohol->aldehyde->carboxylic acid. The order of reactivity goes aldehyde > alcohol > alkane, which is why you typically can't produce aldehydes from alcohols or alkanes unless you can find a way to remove them from the system as they're formed. The pdf you posted actually states that you can oxidize toluene with sodium hypochlorite and steam distill benzaldehyde off as it's formed. A long time ago a small scale experiment was ran - just an impulsive qualitative test - 30% H2O2 was magnetically stirred at high speed with toluene, and the strong, distinct odor of benzaldehyde was noted. It IS a stepwise reaction with most oxidants, it is doubtful KMnO4 is an exception - if it is, please provide a reference providing the mechanism.

As for the issue with water, perhaps the KMnO4 could be dissolved in glycerol for the addition? ...HA! Kidding of course. But maybe there is another solvent that can be used outside of water, and MgSO4 in the RB to absorb water formed from the oxidation. KMnO4 is stable in acetone at r.t., but it seems doubtful this would remain true at elevated temperatures, and the acetone forms an addition product with NaHSO3. It seems like this may be a nonstarter after all - again, this is why it was posted. Thank you to those who provided helpful criticism.

Do you have a reference for NaHSO3 not forming an addition product outside of aqueous solution? Never heard of this.

Not a member of the new generation... been around since the Hive days, just a new moniker now. Please... the insulting tone is not necessary or helpful. This was just an idea that was posted for helpful criticism, to see if anyone could come up with a way to make it workable. Got a graduate education in chemistry but we all make mistakes especially with the influence of the substances we all enjoy. Let's keep this cordial, there is no need for hostility, we are all out to achieve the same goals and on the same side.

lugh · « **Reply #17 on:** March 11, 2012, 04:33:37 AM »

Quote

Do you have a reference for NaHSO3 not forming an addition product outside of aqueous solution?

The bisulfite ion is a nucleophile as explained in the article uploaded in:

http://127.0.0.1/talk/index.php/topic,2505.msg25400.html#msg25400

which should be downloaded and studied by anyone interested in the subject of this thread

You can convert your benzoic acid into benzaldehyde using the process from:

Applied Catalysis A: General 220 41–49 (2001)

Deoxygenation of benzoic acid on metal oxides
1. The selective pathway to benzaldehyde
M.W. de Lange, J.G. van Ommen, L. Lefferts

no1uno · « **Reply #18 on:** March 11, 2012, 04:39:28 AM »

it's all good AF, trouble is Lugh forgets that the old generation didn't do the reading either (including yours truly:P). It's a side effect of getting old I believe, the old "back when I was a lad..." Personally I think there is less tolerance for half-baked ideas now then there was, which can be good and bad, fact is some of the wilder hairs (but by no means a significant percentage) are now bearing fruit and the reasons for the proposed syntheses working can be traced, not without a lot of effort, back to long forgotten journal articles where the real old school chemists came across the same anomalous results and investigated them.

However, it is well known that oxidation of toluene with KMnO4 is a bloody effective way to make benzoic acid, working out how to stop the reaction, or remove a partially oxidised product (and one that is oh so easily oxidised further) from the brew is going to be less than trivial, but we all need a hobby. Given the ease with which BnOH or BnOBz can be purchased, allowing for more selective oxidations (and given the scale of most reactions) I cannot see much point in using a sledgehammer to crack a nut - but then again, I cannot see the point in driving with both hands on the wheel.

Each to their own, personally I find it instructive to see how successive generations (not picking anyone - just observing) solve, or attempt, to solve the same raft of problems. I often wonder, just how much different the world would be and what outlandish results would exist, if older folks just allowed people to reinvent the wheel periodically.

lugh · « **Reply #19 on:** March 13, 2012, 03:37:27 AM »

A good thread started by the much maligned UF about practical benzaldehyde synthesis:

https://the-collective.ws/forum/index.php?topic=7071.0;all

Author Topic: Easy OTC benzaldehyde? (Read 804 times)

Assyl Fartrate

Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Vesp

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Sedit

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Vesp

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

atara

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

Assyl Fartrate

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?

no1uno

Re: Easy OTC benzaldehyde?

lugh

Re: Easy OTC benzaldehyde?